gitlab-org--gitlab-foss/doc/development/verifying_database_capabilities.md

Verifying Database Capabilities

Sometimes certain bits of code may only work on a certain database and/or version. While we try to avoid such code as much as possible sometimes it is necessary to add database (version) specific behaviour.

To facilitate this we have the following methods that you can use:

• Gitlab::Database.postgresql?: returns true if PostgreSQL is being used
• Gitlab::Database.mysql?: returns true if MySQL is being used
• Gitlab::Database.version: returns the PostgreSQL version number as a string in the format X.Y.Z. This method does not work for MySQL

This allows you to write code such as:

if Gitlab::Database.postgresql?
  if Gitlab::Database.version.to_f >= 9.6
    run_really_fast_query
  else
    run_fast_query
  end
else
  run_query
end